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I might as well get back in here with both feet.
'72 FX Eng., Primary case venting??
I've saw in the shop manuals about the primary case needing to be airtight & actually have a partial vacuum when running. Does anyone know FOR SURE why this is required. I've come up with an engine vent setup that dumps that spit oil back into the primary case where it can be returned back to the engine. This setup vents the primary case to atmoshere. I've pulled the primecase inspection(chain adj.) plate and verified primary oiler works without the vacuum and run the bike out for a few miles & didn't notice anything else unusual, except that the engine venting was now oil-less as I desired. Am I going to go blind or sterile without an airtight primary case??
Thanks for any help here...
 

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The sealed primary case allows the engine vacuum to evacuate the oil that is dripped on the primary chain. If there is an air leak, there is potential for the oil to build up in there and cause clutch slippage (dry clutch). Factory spec is something like no more than 6oz. of oil in the primary.


Hope this helps.



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Vent

baggersport said:
The sealed primary case allows the engine vacuum to evacuate the oil that is dripped on the primary chain. If there is an air leak, there is potential for the oil to build up in there and cause clutch slippage (dry clutch). Factory spec is something like no more than 6oz. of oil in the primary.


Hope this helps.



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Baggersport is 100% correct.
If, in fact you do not want the potential of clutch fibers of primary chain filings running through your engine, you can block it off, and let it run in it's own dedicated fluid. Use the feed oil hose as a vent to the outside.
Scott
 

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Discussion Starter #4
Again, thanks fellas for the replies here.
Further running has show some moisture build up in primary case with my revised breather. I guess the blowby is creating this - esp. short trips.
Anyway, I'm working on a change that my be better - problem is, most any oil collecting/condensing setup also tends to collect the moisture in the blowby.
Until I come up with something to address this, I've reverted to the stock setup.
Best to ya ...John H.
 

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Scott-

As a follow-up to your suggestion for totally blocking off the oil feed to the primary, what would you suggest in terms of oil volume to be added to the primary to keep everything adequately lubed?
 
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